The present invention relates to a gas-operated generator heater, having a thermoelectric energy converter in a heater housing, in which combustion air can be introduced from the surroundings and a gas-air mixture can be supplied to a burner via a blower with a downstream mixing device, with the blower taking in combustion air out of the heater housing and the gas being capable of being supplied to the mixing device, while the heat produced by the burner can be conducted to the thermoelectric energy converter for conversion into electrical energy and the part of the thermoelectric energy converter to be cooled is also cooled.
In known generator heaters of this type, the thermoelectric energy converter generates current. The energy conversion is subject to losses. The waste heat arising must be dissipated outside the thermoelectric energy converter in order to protect it from overheating. Resonant machines which are coupled with linear generators are preferred thermoelectric energy converters. These linear generators are surrounded by a cooling coil in which water circulates and are thereby cooled.
These types of water-cooled devices are not only costly to manufacture, they also restrict the system design. Also, significant costs and technical risks are associated with water cooling, of which those associated with the seals shall be mentioned. In addition, access to the converter for maintenance or repair is difficult.
It is an object of the present invention to simplify the design of a gas-operated generator heater in such a way that the design does not require water cooling of the converter and thus eliminates the associated costs and risks.
This object is achieved according to the present invention in that the part of the thermoelectric energy converter to be cooled is surrounded by a pot-shaped cooling tank, to which the combustion air can be supplied from the surroundings in the bottom area, and the combustion air warmed by this part flows via the open top of the cooling tank into the heater housing.
With this design of the heater, the combustion air supplied to the heater housing from the surroundings is ingeniously used for cooling of the thermoelectric energy converter before flowing into the heater housing and being taken in through the blower. Because the blower takes in the combustion air from the heater housing, a partial vacuum arises in the housing which is sufficient for the surrounding air to flow into the heater housing via the cooling tank. The surrounding air taken in enters the cooling tank in the bottom area at ambient temperature, flows around the part of the thermoelectric energy converter to be cooled and, having been heated, exits via the open top of the cooling tank into the heater housing. Due to the largely convective heat conduction, a free flow occurs which reinforces the forced flow. The blower therefore supplies the burner with heated combustion air. The waste heat of the converter is thus utilized and remains in the system. The blower generates a pressure in the heater housing which is lower than the pressure of the surrounding air. The pressure in the cooling tank is lower than the pressure of the surrounding air, but is higher than the pressure in the heater housing, so that an air flow arises from the surroundings into the cooling tank and from there into the heater housing.
The cooling tank only has the function of guiding the flow and can therefore be economically manufactured with thin walls, coarse tolerances, and inexpensive material. The requirements for pressure sealing of the cooling tank are low because the pressure differences between the inside and the outside of the tank are also low. Cable bushings and similar parts are not required in the cooling tank, and the exit of the heated combustion air into the heater housing is completely non-critical.
The surrounding air taken in is supplied to the cooling tank in its bottom area. The combustion air can be supplied axially in the bottom area of the cooling tank or the combustion air can be supplied tangentially over the bottom of the cooling tank, in order to uniformly distribute the surrounding air taken into the cooling tank.
According to one embodiment, the gas-operated generator heater is designed in such a way that the combustion gas of the burner transfers the heat to a Stirling engine of the thermoelectric energy converter and the part to be cooled in the cooling tank is implemented as a linear generator.
Furthermore, for the provision of heated service water, a heat exchanger via which heated service water can be removed is connected between the burner and the waste gas outlet.
A portion of the waste heat in the waste gas can be kept in the system by leading the supply of combustion air through at least a part of the waste gas outlet area before it discharges into the cooling tank.